US3613003A - Transceivers with calling devices - Google Patents

Transceivers with calling devices Download PDF

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Publication number
US3613003A
US3613003A US846170A US3613003DA US3613003A US 3613003 A US3613003 A US 3613003A US 846170 A US846170 A US 846170A US 3613003D A US3613003D A US 3613003DA US 3613003 A US3613003 A US 3613003A
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Prior art keywords
transistor
receiving
amplifier
calling
signal
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Expired - Lifetime
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US846170A
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English (en)
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Mutsuo Kubo
Takeshi Kinoshita
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Toshiba Corp
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Tokyo Shibaura Electric Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
    • H04B1/40—Circuits
    • H04B1/44—Transmit/receive switching

Definitions

  • a transceiver was often provided with a device providing a call signal of a single frequency.
  • a call signal of a single frequency it is not only difficult to identify whether the call signal is sent from a particular remote office or not, but also the sound produced by the call signal is monotonous.
  • a calling device incorporated with relay means and the like to produce a call signal of multiple frequencies is not suitable for use in transceivers because of its large and complicated construction.
  • a device has been proposed wherein the oscillation frequency of an oscillator is varied by means of a switching element, such a device has not been actually utilized as the calling device for the transceiver.
  • a transceiver with a calling device comprising a control signal generator, means for shaping the waveform of a control signal generated by the control signal generator, switching means by a signal shaped by the waveform shaping means, an oscillator and means controlled by the switching means to vary the constant of the oscillation element of the oscillator.
  • FIGS. 1 and 2 are connection diagrams helpful to explain the principle of this invention
  • FIG. 3 illustrates a connection diagram of a transceiver provided with a calling device of the most simple construction
  • FIG. 4 shows a connection diagram of a modified embodiment of this invention wherein a source of control signal for the calling device is formed by a portion of the circuit of receiving equipment;
  • FIG. 5 is a circuit diagram showing the detail of a portion of the transceiver shown in FIG. 4;
  • FIG. 6 is a block diagram of a further modification of this invention.
  • FIG. 7 shows the details of a portion of the circuit shown in FIG. 6;
  • FIG. 8 is a block diagram of a still further modification of this invention.
  • FIG. 9 shows the details of a portion of the circuit shown in FIG. 8.
  • transistors Tr, and Tr are connected in an emitter grounded configuration. Collector electrodes of these transistors are connected to a positive source +Vcc respectively through resistors R, and R while their base electrodes to the same source respectively through resistors R and R A condenser C, is connected between the collector electrode of transistor Tr, and the base electrode of transistor Tr and a condenser C, is connected between the collector electrode of transistor Tr and the base electrode of transistor Tr,.
  • these transistors comprise an astable multivibrator circuit.
  • a collector electrode of a transistor Tr is connected to the positive source +Vcc via a collector bias resistor R,, and a series circuit including a condenser C, and a resistor R, is connected between the collector electrode of transistor Tr, and the ground.
  • the juncture between condenser C, and resistor R is grounded through a series circuit including a condenser C and a resistor R
  • the juncture between condenser C and resistor R is connected to the base electrode of transistor Tr, via serially connected condensers C and C,, a juncture A between these condensers being connected to the positive source +Vcc through a resistor R and to the collector electrode of a transistor Tr via resistor R
  • Both transistors Tr, and Tr are of emitter grounded con figuration and the base electrode of transistor Tr, is connected to the collector electrode of transistor Tr: via an integrating circuit consisting of a resistor R and a condenser C;,.
  • the circuit associated with transistor Tr composes a CR oscillator including a CR phase-shifting circuit, the phaseshifting constant of the CR oscillator being varied by the switching function of transistor Tr,.
  • the astable multivibrator circuit comprising transistors Tr, and Tr, oscillates pulses having a periodic rectangular waveform.
  • transistors Tr, and Tr provide an output pulse of rectangular waveform.
  • Transistor Tr alternately becomes ON and OFF with reference to a predetermined level of the sawtooth wave.
  • the resistance of the collector-emitter path thereof is very high so that only the resistor R is connected between juncture A and the ground.
  • the constant of the phase-shifting circuit or of the positive feedback circuit of the CR oscillator is varied whereby the oscillator generates an oscillation signal, the frequency of which periodically varies between two frequencies depended upon ON and OFF states of transistor Tr,.
  • FIG. 2 illustrates a circuit for generating a call signal having three discrete frequencies which is similar to that shown in FIG. 1 except that the output from the astable multivibrator circuit is supplied to switching transistors Tr, and Tr, respectively through different integrating circuits.
  • a resistor R is connected between the collector electrode of transistor Tr, and the base electrode of transistor Tr while a condenser C is connected between the base electrode of transistor Tr, and the ground.
  • Condenser C a and resistor R, compose a first integrating circuit.
  • a resistor R is connected between the collector electrode of transistor Tr and the base electrode of transistor Tr, whereas a condenser C is connected between the base electrode of transistor Tr and the ground.
  • the condenser C, and resistor R compose a second integrating circuit, and across the collector electrode of transistor Tr, and a juncture B is connected a resistor R corresponding to a resistor R connected to juncture A.
  • the output from the astable multivibrator functions to render transistors Tr, and Tr, alternately ON and OFF.
  • the constant of the phase-shifting circuit adapted to produce the call signal is varied by the following factors.
  • resistor R Between juncture A and the ground is connected only resistor R, while resistor R alone is connected between juncture B and the ground.
  • connection is identical to that of 2.
  • the calling device is comprised by a source of control signal such as an astable multivibrator, a waveform-shaping circuit for converting a signal from the source of control signal into a waveform signal of various types, such as an integrating circuit, a differentiating circuit and the like, an electronic switching means for effecting switching operation in accordance with the signal shaped by the wave-shaping circuit and oscillator means including a plurality of oscillation elements, the constants thereof being varied by the electronic switching means for determining oscillation frequencies.
  • a source of control signal such as an astable multivibrator
  • a waveform-shaping circuit for converting a signal from the source of control signal into a waveform signal of various types, such as an integrating circuit, a differentiating circuit and the like
  • an electronic switching means for effecting switching operation in accordance with the signal shaped by the wave-shaping circuit and oscillator means including a plurality of oscillation elements, the constants thereof being varied by the electronic switching means for determining oscil
  • the transceiver shown in FIG. 3 comprises a transmitting and receiving antenna 1, a receiving equipment 2, a transmitting equipment 1;, a combined audiofrequency power amplifier and modulator 4, a combined loudspeaker and microphone 5 and a calling device Q.
  • Calling device Q comprises a control signal generator 7 such as an astable multivibrator, a switching circuit 8 rendered N and OFF states by a signal supplied from control signal generator 7, and an oscillator 9, the constant of the oscillation elements thereof being varied by the switching circuit 8.
  • switch S After elapse of a predetermined interval of time after transmission of the call signal, switch S is opened to transmit a voice signal to the combined audiofrequency amplifier and modulator 4 through combined loudspeaker and microphone 5, transmissionreception transfer switches 8 -3, 5,-2 and calling switch S Also the voice signal is modulated by combined audiofrequency power amplifier and modulator 4 and is then supplied to transmitting equipment 3 through transmission-reception transfer switch 5 -4. After being multiplied and amplified in the amplifier-modulator 4, the modulated voice signal is radiated through the air by antenna 1 via transmission-reception transfer switch S,-l. On the receiving party, transmissionreception transfer switches 5 -1, 5 -2, 8 -3 and 5 -4 are thrown to the reception side R and calling switch S to the off side.
  • a transmitted radio wave is received by antenna 1 and is supplied to receiving equipment 2 through transmission-reception transfer switch 8
  • a received signal is conducted for amplification to a combined audiofrequency power amplifier and modulator 4 through transmission-reception transfer switch 5,-2, and calling switch S
  • the amplified signal is supplied via transmission and reception transfer switch 5 -3 to combined speakermicrophone 5 which gives forth a calling tone and sequentially a voice. Therefore the receiving party is allowed to identify the transmitting party by distinguishing the calling signal and communicate therewith.
  • FIG. 4 shows a modified embodiment of this invention wherein instead of providing an independent control signal source for the calling device, the control signal source is comprised by a portion of the circuit of the receiving equipment.
  • the transceiver shown in FIG. 4 comprises a transmitting and receiving antenna 11, a receiving equipment l 2, a transmitting equipment Q, a combined audiofrequency power amplifier and modulator 14, a combined loudspeaker and microphone 15, a switching circuit 18, and a combined audiofrequency amplifier and oscillator 19.
  • the switching operation between the transmitting and receiving equipments effected by transmission-reception transfer switches S -l, 8 -2, S 3 and S 4 while the operation of the calling device is performed by calling switches S -l, 8 -2 and 8 -3.
  • Receiving equipment L2 is of the well-known superheterodyne type comprising a highfrequency amplifier 21, a frequency converter 22, a first and a second intermediate-frequency amplifiers 23 and 24 and a detector 25
  • a handy transmitter and receiver such as a transceiver is of the press talk type operated by a pushbutton so that during transmission the receiving equipment is inoperative.
  • it is constructed such that intermediate-frequency amplifiers 23 and 24 may be used as the control signal generator included in the transmitting equipment. More specifically, upon throwing calling switches 8 -1 and 8 -2 to the call side, intermediate-frequency amplifiers 23 and 24 are changed into a control signal generator whereas when call switches 5 -1 and 5 -2 are opened they act as the intermediate-frequency amplifiers.
  • the oscillator 19 of the calling device is constructed such that it is used not only during calling but also during reception as the audiofrequency amplifier by throwing transmission-reception transfer switch 5 -2 and calling switch 8 -3 to the reception side R and off side respectively.
  • FIG. 5 shows the detail of the essential portion of the transceiver shown in FIG. 4.
  • circuits associated with transistors Tr and Tr compose a combined intermediatefrequency amplifier and control signal generator. More particularly, when calling switches 8 -1 and 8 -2 are thrown to the call side, resistors R and R are connected to act as the base bias resistors of transistors Tr and Tr respectively, so that they correspond to resistors R and R in the astable multivibrator circuit shown in FIG. 1.
  • condenser C connected between an intermediatefrequency transformer IFT, and calling switch 5 -2 corresponds to condenser C connected between the collector electrode of transistor Tr and the base electrode of transistor Tr of the astable multivibrator circuit shown in FIG. 1.
  • condenser C connected between an intermediatefrequency transformer IFT; and calling switch 8 corresponds to condenser C shown in FIG. 1.
  • FIG. 5 Since, the switching circuit shown in FIG. 5 is identical with that shown in FIG. 1, corresponding elements are designated by the same reference characters. However, in FIG. 5 between resistor R and condenser C is included a calling switch S 3 which when opened renders the circuit associated with transistor Tr, to operate as an audiofrequency amplifier.
  • the voice signal After being amplified by transistor Tr the voice signal is then coupled to combined audiofrequency power amplifier and modulator 14 and is then radiated from combined transmitting and receiving antenna 11 through transmission-reception transfer switch 8 -4, transmitting equipment l 3 and transmissionreception transfer switch 8,, -l in the same manner as the calling signal.
  • the electromagnetic wave On the receiving party, the electromagnetic wave is received by the combined transmitting and receiving antenna Ill and after being detected by the receiving equipment 1 2, the received signal is supplied to the combined loudspeaker and microphone 15 through transmission-reception transfer switch S -Z, calling switch 8 -3, combined audiofrequency amplifier and oscillator 19, combined audiofrequency power amplifier and modulator 14 and transmission-reception transfer switch S 3. It is also possible to constitute a modification of the circuit shown in FIG. 5 by using the principle circuit shown in FIG. 2, which provides a call signal of three frequencies.
  • the transceiver comprises a combined transmitting and receiving antenna 31, a receiving equipment 32, a transmitting equipment 3 3, a combined audiofrequency power amplifier and modulator 34 and a combined loudspeaker and microphone 35 and the switching between transmitting and receiving equipment is effected by the operation of transmission-reception transfer switches S;,,-1, S 2, S -3, S -4 and 8 -5. Similar to FIG.
  • the receiving equipment 3 2 comprises a high-frequency amplifier 41, a frequency converter 42, intermediate-frequency amplifiers 43 and 44 and a detector 45, the intermediate-frequency amplifier 43 being connected to a control device 4 0, which in turn is connected to a combined audiofrequency amplifier and oscillator 39 via transmission-reception transfer switch S -2 to control the operation of the combined audiofrequency amplifier and oscillator 39.
  • a control signal generator 37 is connected to a switching circuit 38 connected to a combined audiofrequency amplifier and oscillator 39.
  • the switching operation of the calling device is performed by a calling switch S
  • FIG. 7 shows the detail of a portion of the circuit shown in FIG. 6.
  • the emitter electrode of transistor Tr forming the intermediate-frequency amplifier 43 shown in FIG. 6 is connected to the control device Q.
  • Control device 4A comprises switching transistors Tr and Tr and a diode D and operates to control the combined audiofrequency amplifier and oscillator 39. More particularly, the emitter electrode of transistor Tr is grounded through a variable resistor VR, a movable terminal thereof being connected to the base electrode of transistor Tr Both transistors Tr, and Tr are of the emitter grounded configuration while the collector electrode of transistor Trzg is directly coupled to the base electrode of transistor Tr and to the positive source +Vcc via a collector bias resistor R The collector electrode of the other transistor Tr is connected to the source +Vcc via a collector bias resistor R and to diode D which in turn is connected to the emitter electrode of transistor Tr, forming the combined audiofrequency amplifier and oscillator 39.
  • transistor TR is turned ON whereas transistor Tr is turned OFF due to the voltage drop across resistor R
  • Nonconduction of transistor Tr applies a forward bias to diode D and a current is caused to flow through emitter resistor R of transistor Tr through the transmission-reception transfer switch S -2 to out 01f the operation of the combined audiofrequency amplifier and oscillator 39.
  • control device is analogous to that of a squelch circuit commonly utilized in an FM receiver or a receiver with an AGC in order to avoid extremely large noise which appears on the output side of the receiver when received input signal disappears.
  • the calling signal having multiple frequencies is generated by the loudspeaker so that during an interval in which there is received input the audiofrequency amplifier is rendered operative to send out the voice signal through the loudspeaker.
  • FIGS. 6 and 7 operate as follows:
  • the condition of switching circuit 38 is altered by a signal from control signal generator 37 to cause combined audiofrequency amplifier and oscillator 39 to form the required calling signal.
  • This calling signal is modulated by the combined audiofrequency power amplifier and modulator 34, multiplied and amplified by transmitter equipment Q through transmissiomreception transfer switch S -5 and is then radiated into the air from combined transmitting and receiving antenna via transmission-reception transfer switch 5 -1.
  • the electromagnetic wave sent from the transmitting party is received by antenna 31 and supplied to receiving equipment 3 2 through transmission-reception transfer switch S -l.
  • receiving equipment 3 2 highfrequency amplification, intermediatefrequency amplification and detection operations are performed.
  • the calling signal sent from the transmitting party and the AGC signal appear across output terminals of detector 45.
  • the call signal is supplied to the base electrode of transistor Tr, forming combined audiofrequency amplifier and oscillator 39 through transmission-reception transfer switch S -3, calling switch S 2 and condenser C
  • the AGC signal is applied to the base electrode of transistor Tr forming an intermediatefrequency amplifier through resistor R so that the emitter voltage of transistor Tr will be decreased.
  • the transistor Tr is maintained in its nonconductive condition by the voltage drop across resistor R
  • transistor Tr is rendered conductive by the AGC signal
  • the amplified call signal is applied to combined loudspeaker and microphone 35 to generate the calling tone.
  • this wave On the receiving party this wave is received by transmission and receiving antenna 31, and is then subjected to highfrequency amplification, frequency conversion, intermediatefrequency amplification and detection operations in the receiving equipment 32, and only the AGC signal is produced across output terminals of detector 45 in the receiving equipment 32,. Similar to the case (1) this AGC signal actuates control device to turn on transistor Tr of the combined amplifier and oscillator 39. At this time, since calling switch S on the receiving party is thrown to CALL side, the combined audiofrequency amplifier and oscillator 39 operates as an oscillator.
  • the condition of the switching circuit 38 is varied according to the signal produced by control signal generator 37 so that combined audiofrequency amplifier and oscillator 39 operates to form a predetermined call signal which is applied to combined loudspeaker and microphone 35 through combined power amplifier and modulator 34, and transmissio n-reception transfer switch s,, -4 to produce a calling tone.
  • control signal generator 37 so that combined audiofrequency amplifier and oscillator 39 operates to form a predetermined call signal which is applied to combined loudspeaker and microphone 35 through combined power amplifier and modulator 34, and transmissio n-reception transfer switch s,, -4 to produce a calling tone.
  • identification can be made in an effective manner.
  • this system it is possible to produce a comfortable calling tone with a simple construction.
  • the transmitting party operates in the same manner as in case 1 while the receiving party operates in the same manner as in case (2).
  • the receiving party can immediately respond by merely throwing transmission-reception transfer switch S to the transmission side T without the necessity of operating the calling switch S It may be possible to determine which one of above-described calling operations (I), (2) and (3) should be selected and such selection may be made depending upon the condition of the propagation.
  • control device operates in a manner similar to a squelch circuit so that the loudspeaker does not generate any undesirable noise during waiting time.
  • FIG. 8 is the block diagram and FIG. 9 represents the concrete circuit arrangement of a still further embodiment of this invention, in which the control signal generator 37 in the embodiments shown in FIGS. 6 and 7 is constructed using, as shown in FIGS. 4 and 5, first and second intermediatefrequency amplifiers 23 and 24, which are not required at the receiving time.
  • the same parts of receiving equipment Q as those of the similar equipment of FIGS. 4 and Sara denoted by the same reference numerals and the parts of other equipments than said receiving equipment Q are represented by the same reference numerals as are used in FIGS. 6 and 7 and concrete description thereof is omitted.
  • the transceiver is practicable only in the case where on the transmitting party calling switches S -l, S 2, 8 -1 and Sag-2 are thrown to the CALL side and a transmission-reception transfer switch S is thrown to the transmission side T and on the receiving party calling switches 5 -1, 8 -2, Sag-1 and S -2 are thrown to the OFF side and transmission-reception transfer switch S is thrown to the receiving side R. Accordingly, it is not possible to derive the calling tone of the receiving party from the combined loudspeaker and microphone 35 as in FIGS. 6 and 7, thus eliminating the necessity of providing any extra control signal generator.
  • this invention provides a transceiver including a calling device capable of forming a call signal of multiple frequencies with simple construction thus enabling easy identification of the remote calling party. Further, as the call signal comprises multiple frequencies it is possible to produce comfortable tone, in some case constituting a unique melody.
  • a transceiver comprising:
  • receiving equipment means connected to said antenna receiving a transmitted signal through said antenna, said receiving equipment comprising a cascade connection of a high-frequency amplifier, a frequency converter, a first and second intermediate-frequency amplifier and a detector;
  • transmitting equipment means connected to said antenna transmitting a signal via said antenna
  • a transmission-reception transfer switch including a reception side and a transmission side according to a receiving time and a transmitting time connected to supply a bias voltage to said receiving or transmitting equipment means;
  • a calling device including an output terminal generating a call signal of multiple tones consisting of a control signal formed using said receiving equipment, a switching circuit including ON or OFF condition controlled by said control signal, and an oscillation circuit including oscillation elements connected to said switching circuit in which the constant of the oscillation elements is varied by said switching circuit;
  • a combined audio amplifier and modulator having an input terminal connected to the output terminal of said calling device including amplifying and modulating means performing an amplifying operation at the receiving time and a modulating operation at the transmitting time;
  • a combined loudspeaker and microphone connected to said combined audio amplifier and modulator, from which a calling tone and voice is derived at the receiving time and to which a voice is supplied at the transmitting time.
  • control signal generator of said calling device is so adapted and disposed as to use said first and second amplifiers, and said oscillation circuit is so adapted and disposed as to operate as an audiofrequency amplifier at the receiving time.
  • control signal generator of said calling device comprises an astable multivibrator constructed using a transistor involved in said first and second intermediate-frequency amplifiers respectively and an integral circuit shaping the waveform of an output signal from said multivibrator.
  • said receiving equipment comprises a cascade connection of a high-frequency amplifier, a frequency converter, a first and second intermediate-amplifier and a detector so as to form an AGC circuit transferring an AGC signal derived from the output terminal of said detector to the input terminal of said first intermediatefrequency amplifier
  • said control signal generator of said calling device comprises an astable multivibrator and an integral circuit shaping the waveform of an output signal from said multivibrator
  • said switching circuit comprises a first transistor to the base of which there is supplied an output signal from said integral circuit to control said transistor to an ON or OFF condition
  • said oscillator comprises a CR phase shift oscillator whose impedance is varied according to the ON or OFF condition of said transistor and a second transistor, thereby to oscillate a call signal of multifrequencies and operate as an audiofrequency amplifier at the receiving time
  • said transceiver further comprising a control device having an input terminal connected to said first intermediate-frequency amplifier and an output tenninal connected to said combined audiofrequency amplifier and
  • a transceiver comprising:
  • receiving equipment means connected to said antenna receiving a transmitted signal through said antenna, said receiving equipment comprising a cascade connection of a high-frequency amplifier, a frequency converter, a first and second intermediate amplifier and a detector so as to transfer a detecting signal derived from the output terminal of said detector to the input terminal of said first intermediate frequency amplifier;
  • transmitting equipment means connected to said antenna transmitting a signal via said antenna
  • a transmission-reception transfer switch including a reception side and a transmission side according to a receiving time and a transmitting time connected to supply a bias voltage to said receiving or transmitting equipment means;
  • a calling device including an output terminal generating a call signal of multiple tones consisting of a control signal generator generating a control signal, a switching circuit controlled to an ON or OFF condition by said control signal, and an oscillation circuit including oscillating elements connected to said switching circuit, in which the constant of the oscillation elements is varied by said switching circuit;
  • a combined audio amplifier and modulator having an input terminal connected to the output terminal of said calling device including amplifying and modulating means, performing an amplifying operation at the receiving time and a modulating operation at the transmitting h.
  • a cdntrol device having an input terminal connected to said first intermediate-frequency amplifier and an output terminal connected to said combined audiofrequency amplifier and oscillator only at the receiving time, and performing such a squelch operation as stops the operation of said audiofrequency amplifier when there does not appear said detecting signal;
  • control signal generator of said calling device comprises an astable multivibrator and an integrating circuit shaping the waveform of an output signal from said multivibrator
  • said switching circuit comprises a first transistor to the base of which there is supplied an output signal from said integrating circuit to control said transistor to an ON or OFF condition
  • said oscillator comprises a CR phase shift oscillator whose impedance is varied according to the ON or OFF condition of said transistor and a second transistor, thereby to oscillate a call signal of multifrequencies and operate as an audio frequency amplifier at the receiving time.

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US846170A 1968-08-05 1969-07-30 Transceivers with calling devices Expired - Lifetime US3613003A (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3758860A (en) * 1972-01-17 1973-09-11 Motorola Inc Selective calling squelch circuit for receiving systems
USRE28745E (en) * 1971-12-07 1976-03-23 Carson Manufacturing Company, Inc. Electronic Siren Circuit
US4060764A (en) * 1976-03-25 1977-11-29 Motorola, Inc. Transceiver audio system
US4060765A (en) * 1975-08-20 1977-11-29 Sanyo Electric Co., Ltd. Press-to-talk transceiver
US4184115A (en) * 1976-03-26 1980-01-15 Clarion Company Limited Mobile citizen band transceiver control unit with an audio frequency apparatus
US4225821A (en) * 1977-11-28 1980-09-30 Carleson Donald V Electronic signalling device to alert CB radio equipped vehicles

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2883459A (en) * 1957-09-20 1959-04-21 Roy Yvon Carrier-current intercommunication system
US3038070A (en) * 1958-05-26 1962-06-05 Westinghouse Electric Corp Radio receiver apparatus
US3054971A (en) * 1959-11-10 1962-09-18 Westinghouse Electric Corp Frequency shift oscillator
US3160877A (en) * 1960-11-29 1964-12-08 Charbonnages De France High-pitched horn
US3292085A (en) * 1963-09-18 1966-12-13 Motorola Inc Combined encoder-decoder device providing rapid build up of oscillations
US3339141A (en) * 1964-09-11 1967-08-29 Rothenbuhler Eng Co Two-tone remote control system
US3488593A (en) * 1964-11-30 1970-01-06 Victor Company Of Japan Frequency converter circuit changeable to an audio frequency amplifier

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2883459A (en) * 1957-09-20 1959-04-21 Roy Yvon Carrier-current intercommunication system
US3038070A (en) * 1958-05-26 1962-06-05 Westinghouse Electric Corp Radio receiver apparatus
US3054971A (en) * 1959-11-10 1962-09-18 Westinghouse Electric Corp Frequency shift oscillator
US3160877A (en) * 1960-11-29 1964-12-08 Charbonnages De France High-pitched horn
US3292085A (en) * 1963-09-18 1966-12-13 Motorola Inc Combined encoder-decoder device providing rapid build up of oscillations
US3339141A (en) * 1964-09-11 1967-08-29 Rothenbuhler Eng Co Two-tone remote control system
US3488593A (en) * 1964-11-30 1970-01-06 Victor Company Of Japan Frequency converter circuit changeable to an audio frequency amplifier

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE28745E (en) * 1971-12-07 1976-03-23 Carson Manufacturing Company, Inc. Electronic Siren Circuit
US3758860A (en) * 1972-01-17 1973-09-11 Motorola Inc Selective calling squelch circuit for receiving systems
US4060765A (en) * 1975-08-20 1977-11-29 Sanyo Electric Co., Ltd. Press-to-talk transceiver
US4060764A (en) * 1976-03-25 1977-11-29 Motorola, Inc. Transceiver audio system
US4184115A (en) * 1976-03-26 1980-01-15 Clarion Company Limited Mobile citizen band transceiver control unit with an audio frequency apparatus
US4225821A (en) * 1977-11-28 1980-09-30 Carleson Donald V Electronic signalling device to alert CB radio equipped vehicles

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JPS5821450B2 (ja) ジユシンキ